Recently, there is an increasing interest in polymeric materials having nano-sized spherical structures, and their applications are extended to electro-, bio- and functional polymers and other additives.
According to a recent tendency of reduction in a metal line pitch resulting from high-density integration of semiconductor devices, several problems including propagation delay, cross talk, power dissipation, etc., may occur. To solve such problems, a method of reducing RC (resistance×capacitance) delay may be considered first of all. Particularly, used is a method of reducing resistance of a metal line material and reducing conductance between metal lines. For the purpose of carrying out such a method, copper (Cu) with good conductivity is generally used as a metal line material. Otherwise, materials with good insulation property are generally used between metal lines. Most insulating materials that are currently used are formed of silicon oxides having a dielectric constant of 4.0. Therefore, it is desirable to reduce the dielectric constant to 2.2, preferably to 2.0, or less.
A method for introducing pores into an insulating film has been researched so as to obtain a thin insulating film having a dielectric constant of 2.2 or less. A material used for such pore generation is referred to as a porogen (or pore generator: pore-generating organic polymer), which generates pores particularly by calcination. Linear polymeric polycaprolactone and polyacrylate, branched polyester having multiple side-branches, etc., have been used as pore generators. However, they are not suitable for such use and thus there is a need to improve them.
In the case of branched polymer or dendrimer used for generating pores, it is difficult to control the molecular weight, molecular weight distribution, microstructure, etc., and thus to generate micropores having a uniform size. Additionally, although there is an example that crosslinked nanoparticles have been used to form nanopores, it is also found to be difficult to form nanoparticles having a uniform size. Moreover, there is a possibility of pyrolysis residues being present.